Arsenic et Hydrargyri Hydriodatis Liquor. Solution of Hydriodate of Arsenic and Mercury; Donovan's Solution. (Not officinal.) Prep. (Pure arsenic, in fine powder, six grains: pure mercury sixteen grains; pure iodine, fifty and a half grains; alcohol, half a fluid drachm; distilled water, nine ounces or a sufficient quantity. Rub together the arsenic, mercury, iodine, and spirit, until a dry mass is obtained, and having triturated eight ounces of the water with this in successive portions, let the whole be transferred to a flask, and heated until it begins to boil. When cooled and filtered, let as much distilled water be added to it as will make the bulk of the solution exactly eight fluid ounces and six drachms.) [Liquor Arsenici et Hydrargyri Iodidi. Solution of Iodide of Arsenic and Mercury. 35 grains of the Iodide of Arsenic and the same quantity of the Red Iodide of Mercury are dissolved in half a pint of distilled water. U. S.]

Prop. & Comp. A very pale greenish-coloured liquid, having 6 no odour, but a styptic taste; it probably contains the red iodide of mercury (Hg I) and ter-iodide of arsenic (As I3).

Therapeutics. It has been used chiefly in obstinate skin affections, and seems occasionally to be useful when other preparations of arsenic fail; it is peculiarly applicable to those depending on venereal taint. Externally, freely diluted, it has been used as a lotion in similar cases.

Dose. 10 min. to 1/2 fl. drm. diluted, and given with the precautions enjoined for the other preparations of arsenic. Each fl. drm. contains about 0.086 gr. of metallic arsenic.